Fuel metering pump calibration method

Abstract

A system and method for accurately supplying fuel flow to a gas turbine engine from a fuel metering pump regardless of variations in operating conditions of the fuel metering pump. The system determines an updated flow characteristic curve for an electrically powered positive displacement pump that is configured to supply fluid via a valve that is configured to open at a predetermined fluid inlet pressure. Electrical current is supplied to the pump to thereby cause the pump to supply the fluid to the valve. The electrical current supplied to the pump is monitored to determine when the valve opens, and one or more points on the updated flow characteristic curve are determined based on the determination of when the valve opens.

1. A method of determining an updated flow characteristic curve for an electrically powered positive displacement pump, the pump configured to supply fluid via a valve that is configured to open at a predetermined fluid inlet pressure, the method comprising the steps of:
 supplying electrical current to the pump to thereby cause the pump to supply the fluid to the valve; 
 monitoring the electrical current supplied to the pump to determine when the valve opens; and 
 determining one or more points on the updated flow characteristic curve based on the determination of when the valve opens. 
 
   
   
     2. The method of  claim 1 , further comprising:
 determining a nominal flow characteristic curve of the pump; 
 determining a nominal shift value based on the determination of when the valve opens, the nominal shift value representative of an amount of change from the nominal flow characteristic curve; and 
 applying the nominal shift value to the nominal flow characteristic curve to thereby determine the one or more points on the updated flow characteristic curve. 
 
   
   
     3. The method of  claim 2 , further comprising:
 storing the nominal shift value in a memory. 
 
   
   
     4. The method of  claim 1 , further comprising:
 controllably increasing pump rotational speed to thereby controllably increase pump discharge pressure and the electrical current supplied to the pump. 
 
   
   
     5. The method of  claim 4 , further comprising:
 monitoring pump rotational speed; and 
 determining the pump rotational speed when the valve opens. 
 
   
   
     6. The method of  claim 5 , wherein the updated flow characteristic curve is a flow versus speed curve, and wherein the method further comprises:
 automatically controlling fluid flow by controlling pump rotational speed. 
 
   
   
     7. The method of  claim 5 , further comprising:
 determining a nominal flow versus speed curve for the pump; and 
 determining a nominal shift value based on the determination of when the valve opens, the nominal shift value representative of an amount of change from the nominal flow versus speed curve; and 
 applying the nominal shift value to the nominal flow versus speed curve to thereby determine the one or more points on the updated flow characteristic curve. 
 
   
   
     8. In a fuel supply system that includes an electrically powered positive displacement fuel metering pump in fluid communication with a pressurizing valve that is configured to open at a predetermined inlet pressure, a method of establishing fuel flow to a gas turbine engine during engine startup, comprising the steps of:
 determining a nominal flow characteristic curve of the fuel metering pump; 
 supplying electrical current to the fuel metering pump and controllably increasing its speed to thereby cause the fuel metering pump to supply fuel to the pressurizing valve at an increasing pressure magnitude; 
 monitoring the electrical current supplied to the fuel metering pump to determine when the pressurizing valve opens; 
 determining a nominal shift value based on the determination of when the pressurizing valve opens, the nominal shift value representative of an amount of change from the nominal flow characteristic curve; and 
 controlling fuel flow to the gas turbine engine by applying the nominal shift value to the nominal flow characteristic curve. 
 
   
   
     9. The method of  claim 8 , further comprising:
 monitoring fuel metering pump rotational speed; and 
 determining the pump rotational speed when the pressurizing valve opens. 
 
   
   
     10. The method of  claim 9 , wherein:
 the nominal flow characteristic curve is a flow versus speed curve; and 
 the method further comprises controlling fuel flow to the gas turbine engine by controlling pump rotational speed. 
 
   
   
     11. The method of  claim 8 , further comprising:
 storing the nominal shift value in a memory. 
 
   
   
     12. The method of  claim 8 , further comprising:
 storing a plurality of the nominal shift values in the memory; and 
 determining a health status of the fuel metering pump based at least in part on the stored nominal shift values.